WO2024042241A1

WO2024042241A1 - Control system for a multiphase brushless motor without a position sensor

Info

Publication number: WO2024042241A1
Application number: PCT/EP2023/073444
Authority: WO
Inventors: Christophe AUDOUY
Original assignee: Sonceboz Motion Boncourt Sa
Priority date: 2022-08-25
Filing date: 2023-08-25
Publication date: 2024-02-29
Also published as: FR3139253A1

Abstract

The present invention relates to a control system for a multiphase brushless motor without a position sensor, incorporating drive control electronics, comprising: • - a switching means (20), provided with two-state switches (12 to 17), for varying the electrical voltage applied to each of the phases; • - a means for detecting overloading (32) of the motor; and • - a means for determining an operating point (34), allowing at least two operating points to be applied; • - the control electronics being arranged to use space vector modulation or vector modulation to generate a sinusoidal waveform from a DC voltage, and the control electronics being arranged to modify the operating point at least once if an overload is detected by the overload detection means (20).

Description

Control system intended for a polyphase brushless motor without a position sensor.

Field of the invention

The present invention relates to the field of step-by-step type geared motors (direct current brushless synchronous polyphase motors controlled in a step-by-step mode), and more particularly geared motors controlled in a micro-stepping mode.

The step-by-step control mode leads to increments of rotation, at the level of the rotor, called whole steps, which correspond, for example, to 6 whole steps (respectively 4) per electrical period of the current present in each phase, for a three-phase motor (respectively two-phase). To reduce this rotation increment, for example, to reduce operating noise and vibrations generated at the rotor, the entire steps can be subdivided into micro-steps. To do this, and unlike the whole-step control mode, each of the phases of the motor must then be controlled with a current of approximately sinusoidal shape depending on the number of micro-steps per step. For this purpose, for a three-phase motor, 6 transistors will be necessary to simultaneously impose in the 3 phases of the motor 3 substantially sinusoidal current waves, phase shifted by 120° electrical.

The usual detection methods for stops, or stalling, of stepper geared motors use means for detecting the value of the voltage induced in the phases of the motor, in particular states of the control transistors of these phases (state open for example, allowing the voltage induced in the unused phase to be measured without interference).

We therefore see that for polyphase motors controlled in microstep mode, using all the power transistors simultaneously, it is difficult to have access to this induced voltage measurement.

State of the art

la détermination d'une vitesse de rotor estimée et d'une première valeur de tension de force contre-électromotrice, BEMF, dans une trame de référence associée au rotor estimée au moyen d'un observateur BEMF ;
le calcul d'une deuxième valeur de tension BEMF estimée dans une trame de référence associée au rotor au moins sur la base d'une première constante de moteur et de la vitesse de rotor estimée
la génération d'une valeur de filtre d'erreur BEMF (BEMFErrorFilt) sur la base d'une différence entre les première et deuxième valeurs de tension BEMF estimées ;
la génération d'une valeur de seuil d'erreur BEMF (BEMFErrorThreshold) en fonction de la vitesse de rotor estimée (ω) soumise à une valeur BEMF seuil minimale (BEMFErrorThresholdMin) ; et
la détection d'une condition de blocage du rotor dans le moteur synchrone à aimants permanents sans capteur au moins sur la base de la valeur de filtre d'erreur BEMF (BEMFErrorFilt) et de la valeur de seuil d'erreur BEMF (BEMFErrorThreshold).

We know in the state of the art the patent application US2017126153 describing a method intended to detect a blocking condition of the rotor in a permanent magnet synchronous motor without sensor, comprising:

determining an estimated rotor speed and a first back electromotive force voltage value, BEMF, in a reference frame associated with the rotor estimated using a BEMF observer;
calculating a second estimated BEMF voltage value in a reference frame associated with the rotor based at least on a first motor constant and the estimated rotor speed
generating a BEMF error filter value (BEMFErrorFilt) based on a difference between the first and second estimated BEMF voltage values;
generating a BEMF error threshold value (BEMFErrorThreshold) based on the estimated rotor speed (ω) subject to a minimum BEMF threshold value (BEMFErrorThresholdMin); And
detecting a rotor lock condition in the sensorless permanent magnet synchronous motor based at least on the BEMF error filter value (BEMFErrorFilt) and the BEMF error threshold value (BEMFErrorThreshold).

We also know the patent application EP3826170 describing a stall detector for detecting the stall of a brushless direct current motor. The brushless DC motor is adapted to apply one or more control signals such that currents passing through one or more coils of the brushless DC motor generate a flux for controlling the motor. The stall detector includes a processing device adapted to determine a direct angle between a back electromotive force voltage vector generated by the motor and a current vector which represents the flow generated by the currents through one or more coils. The processing device is further adapted to determine that the engine is stalling when the direct angle exceeds a predefined threshold at least once.

Patent EP2966772 proposes a method for detecting stalling of a two-phase or three-phase motor operating in a microstep mode, the method comprising:

a) applying a plurality of phase-shifted micro-step waveforms (6) to the phase windings (Lu, Lv, lw) of said motor, whereby the phase shift is approximately 120° in the case of a three-phase motor and approximately 90° in the case of a two-phase motor;

b) determining a sum of currents flowing through the phase windings of said motor, and taking samples (Raw) of said sum of currents synchronously with the application of said microstepping waveforms;

c) calculating a moving average (MoAvg) or a moving sum of said samples over a number of samples corresponding to 120° or an even multiple of 60° of the microstep waveform in the case of a three-phase motor and corresponding to 180° or an even multiple of 90° of the microstep waveform in the case of a two-phase motor;

d) calculating an adaptive threshold on the basis of said samples (Raw);

e) detecting motor stall when the moving average (MovAvg) or the moving sum is greater than said adaptive threshold.

Patent application JP2005151678 proposes a device for controlling a permanent magnet synchronous motor without a damper (PM motor) without a position sensor.

Disadvantages of prior art solutions

Some of the solutions of the prior art require one or more position or torque sensors, which increases the manufacturing cost and complicates production.

Other solutions require complex algorithmic processing, involving the use of powerful processors and resulting in high power consumption.

Finally, these solutions lead to untimely shutdowns when the resistance to movement of the driven member increases and exceeds a resistance torque without however characterizing a blockage. This leads to improper positioning, and possibly inappropriate error reporting.

Solution provided by the invention

The object of the present invention is to remedy this drawback and concerns, according to its most general acceptance, a control system intended for a polyphase brushless motor having the technical characteristics set out in claim 1.

un moyen de commutation, munis d’interrupteurs à deux états, destiné à faire varier la tension électrique appliquée à chacune des phases,
un moyen de détection de surcharge du moteur,
un moyen pour la détermination d’un point de fonctionnement, permettant l’application d’au moins deux points de fonctionnement,
ladite électronique de commande étant agencée pour utiliser la modulation de vecteurs d'espace ou modulation vectorielle afin de générer une forme d’onde sinusoïdale à partir d’une tension continue.

The motor does not have a position sensor and incorporates drive control electronics including

a switching means, provided with two-state switches, intended to vary the electrical voltage applied to each of the phases,
a means of detecting motor overload,
a means for determining an operating point, allowing the application of at least two operating points,
said control electronics being arranged to use space vector modulation or vector modulation in order to generate a sinusoidal waveform from a direct voltage.

Said control electronics are arranged to modify the operating point at least once in the event of detection of an overload by the overload detection means.

Advantageously, said blocking detection means comprises a circuit for measuring the total current consumed by the N phases of the motor.

In a variant, said blocking detection means comprises a sampling resistor and means for measuring in said resistance, image of the total current consumed in the sum of the N phases of the polyphase motor.

In another variant, said blocking detection means comprises:

a means of measuring the sum of the currents circulating in each of the phases of the motor,

a means for calculating a stop detection threshold in relation to the evolution of the sum of said currents,

means for processing the current values sampled by a mathematical or statistical operation, the stop detection threshold being determined in relation to the result of this processing.

Advantageously, said overload detection means delivers a signal controlling the modification of the operating point in the event of overload detection during X consecutive iterations, then an instruction to stop the motor in the event of new blocking detection.

In addition, said means for determining an operating point comprises an interface for receiving a signal supplied by an external conditions sensor.

For example, the external conditions sensor is a temperature sensor.

Alternatively, the external conditions sensor provides a measurement of the supply voltage of the switching means.

Detailed description of a non-limiting example of production

Other advantages of the present invention will be easily appreciated, as these become better understood with reference to the following detailed description illustrated by the accompanying drawings in which:

There represents a schematic view of the control circuit for controlling a three-phase BLDC motor,

There represents a schematic view of the “space vector modulation” processing circuit for controlling a three-phase BLDC motor,

There represents the timing diagrams of the signals used for the implementation of the invention,

There represents the timing diagrams of two types of operating points,

There represents an example of a movement start sequence with updating of the operating point upon overload detection.

General principles of the invention

The proposed solution consists of creating a space vector modulation control mode or commonly called “space vector modulation” (SVM) whose operating points can be adapted according to the external load and/or external conditions (example : temperature / voltage).

en augmentant le courant et/ou la tension,
et/ou diminuant la consigne de vitesse,

The principle of the invention consists of providing control electronics arranged to detect an overload by the overload detection means (32) and, in the case of detection of an overload, modify the operating point at least once

by increasing the current and/or voltage,
and/or reducing the speed setpoint,

and in the event of permanent overload detection (32) after a cycle of N iterations, to control the motor to stop, N being greater than 1, in order to avoid constantly calculating the new setpoint via the applications of Park and Clark transforms requiring heavy digital processing.

The general principle of a control circuit for controlling a three-phase BLDC motor connected in star is illustrated by the . A three-phase DC brushless motor comprises three motor windings (1 to 3), designated as phases U, V, W connected in a star network. One end (4 to 6) of each winding (1 to 3) is connected to a termination (7 to 9) respectively. The other ends of the windings (1 to 3) are connected together by a termination (10) to obtain a star connection. The control circuit comprises a switching means (20), here a three-phase bridge. Each arm of the three-phase bridge includes a pair of switches (12 to 17) in the form of an upper transistor and a lower transistor connected in series between a power rail (18) and the ground line (19). . The terminations (7, 8, 9) are electrically connected to the three-phase bridge, respectively between a complementary pair of switches (12, 15; 13, 16; 14, 17). The switches (12 to 17) are turned on and off in a controlled manner by a controller to provide pulse width modulation of the potential applied to each of the terminals (7 to 9), this to control the potential difference applied across each windings (1 to 3) and therefore also the current flowing through the windings (1 to 3) and consequently the strength and orientation of the magnetic field produced by the windings (1 to 3).

Note that the schematizes a three-phase bridge connected to a three-phase winding connected in a star, however this configuration is not limiting to the invention and any other number of phases, or connection of the winding, known to those skilled in the art is considered. For example a motor comprising 12 coils connected in parallel delta, each winding comprising 4 coils connected in parallel, is included in the invention. It is also possible to use a full-bridge inverter, comprising twice as many arms, for which each winding end is connected to an arm of the inverter. The use of multilevel inverters, with more than 2 switches per arm, is also not excluded.

Detailed description of the control circuit « space vector modulation »

There represents a schematic view of the “space vector modulation” processing circuit for controlling a three-phase BLDC motor according to the invention.

The generation of SVM control is carried out via the subassembly (30). For this operation, a pre-programmed vector table can be used for the sub-assembly (37), which does not require significant computing power by bypassing the conventional sinusoidal signal generators (35) and the transformation in the α plane, β produced by the subset (36). The subassembly (38) generating the setpoint signals to the inverter (20) in the form of a PWM command. The subsets (35) to (37) can be grouped within a single subset (39) via a pre-programmed vector switching table.

SVM control is a principle well known to those skilled in the art and makes it possible to generate a sinusoidal phase current from a direct supply voltage by controlling the activation time of each branch of the inverter. The feedback loop is made up of several subassemblies including in particular a current measuring means (31), an overload detection means (32) and a means for correcting the setpoint signal (33). This feedback loop is traditionally made up of sensors or complex algorithms requiring the use of Park, Clarke transformation. A measurement of the phase current / voltage is carried out through the subassembly (31), this data can be used by an overload detection means (32), for example a blocking detection algorithm. Depending on the output signal of the overload detection algorithm, the means for correcting the set signal (33) in current and/or speed transmits the appropriate signal to the means for determining an operating point (34). ). The means for determining an operating point (34) compiles all the data coming from the feedback loop and possibly from external condition sensors (40, 41), for example the temperature or the supply voltage of the the inverter, in order to select the optimal operating point to apply to the system.

Description of the operating point change algorithm

The operating principle of the algorithm is to adapt the operating point dynamically based on the detection of an overload, and optionally, based on external condition data such as temperature, voltage, load, or any other parameter or one of these combinations.

This operating mode avoids the use of digital processing for calculating a Clarke and Park transform, requiring significant computing power, while approaching a behavior similar to the FOC (“Field Oriented Control”) control mode. ").

For this, a blocking detection algorithm is implemented in order to stop the motor before it stalls in the event of a significant external load and to be able to use a new operating point. This algorithm could for example be the algorithm described in patent EP1680862 or any other blocking detection algorithm.

The blocking detection algorithm is normally implemented in order to stop the motor before it stalls in the event of a significant external load. The invention consists of not systematically controlling the stopping of the motor, but of transiently using this information to control a modification of the operating point, possibly in an increasing sequence, before actually controlling the stopping of the motor.

For this purpose, the microcontroller decides before informing of the blocking to restart a movement with an operating point presenting more torque (by reducing the speed and/or increasing the current), after a predefined duration or movement, it can be considered returning to the initial operating point.

If the ^2nd operating point is not sufficient, it is then possible to inform the user (via the ECU in the automotive sector) of the blocking of the actuator or to retry the movement with another operating point .

Depending on the responsiveness of the stop detection algorithm, you can choose to stop, or not, the motor for changing the operating point.

It is also possible to use external conditions to evaluate the operating point to be applied to the motor. This check of external conditions can be carried out before starting the movement or during the movement.

Example: The actuator is able to provide a dynamic torque of 1.5Nm at 4rpm over the entire temperature range but only if the voltage is between 11 and 16V. If the measured voltage is between 9V and 11V, the actuator decides to reduce the speed to 2.25rpm in order to guarantee a torque of 1.5Nm.

Example of operation

Figure 3 represents the timing diagram of the position control signals, position feedback, current and the blocking detection signal. The position command, , is illustrated by the curve (300), the position feedback, , is illustrated by the curve (310), the current measurement, , is illustrated by the curve (320), the measurement of the blocking detection algorithm, , is illustrated by the curve (330). All these curves are represented in arbitrary units, .

During this sequence, a closing command (340) is transmitted to the actuator. During the execution of this closing movement, the actuator detects a blockage (350).

A change of operating point, by reducing the speed for example, is then carried out without reporting an error to the computer. This new operating point allows the movement to continue (360) and resolves the blocking condition detected by the algorithm. After passing the hard point, another operating point (370) can be established in order to complete the movement until the controlled member arrives at the known stop position, at instant (380). The final position being known, the algorithm does not, in this case, adapt the operating point, but simply stops the movement.

Example of point adaptation in operation

Figure 4 represents the timing diagram illustrating the adaptation of the operating point as a function of the inverter supply voltage. The curve (100) illustrates the evolution of the supply voltage of the inverter, , and the curve (200) that of the set speed, .

When using the device, the member connected to the actuator is driven at a nominal speed . The supply voltage of the inverter, then worth , makes it possible to obtain a nominal torque . If, for any reason, the supply voltage drops below the threshold voltage right now (110) . The voltage across the inverter terminals is then no longer sufficient to obtain the nominal torque . The operating point can then be adapted, for example by lowering the speed to a value allowing the nominal torque to be obtained for a voltage greater than . If right now (120) the voltage goes back above the threshold value the speed is again adapted to return to its nominal value . If during the movement the voltage fell below the threshold , the speed would be adapted again to guarantee obtaining the nominal torque . If the voltage drops so that it is no longer possible to obtain the nominal torque, then the algorithm may decide to stop the movement.

Example of operating point adaptation algorithm

There represents in this context an example of a movement start sequence with updating of the operating point upon overload detection.

When the movement is started, the algorithm leaves the initialization block (400) to perform an overload control is implemented, alternating the OL overload detection monitoring block (401) and the MOVE movement block (405 ) via a loop. In the event of overload, the algorithm exits said loop to modify the operating point. The algorithm then joins the block (402) controlling the value of the incremental variable i and, if the threshold movement, via the UPDATE block (403) before proceeding to the increment of said variable i described by the block (404) before returning to the loop monitoring the overload. If the overload condition persists, the algorithm attempts an additional increment of the operating point, within the limit of X attempts. If the overload persists after X updates of the operating point, the algorithm joins block (406) and the motor is stopped.

This sequence is in no way limiting to the invention and the skilled person could imagine other possibilities depending on the goal to be achieved. For example, it is possible to imagine a sequence where the operating point is not gradually increased to provide more torque, but follows an adjustment by dichotomy to optimize the final value.

Claims

Control system intended for a polyphase brushless motor without a position sensor integrating drive control electronics comprising

a switching means (20), provided with two-state switches (12 to 17), intended to vary the electrical voltage applied to each of the phases,

a motor overload detection means (32),

means for determining an operating point (34), allowing the application of at least two operating points.

characterized in that said control electronics is arranged to modify, in the event of detection of an overload by the overload detection means (20), at least once the operating point
said overload detection means (20) delivering a signal controlling the modification of the operating point in the event of overload detection for several consecutive iterations, then an instruction to stop the motor in the event of new blocking detection.
Control system intended for a sensorless polyphase brushless motor according to claim 1 characterized in that said control electronics being arranged to use space vector modulation or vector modulation in order to generate a sinusoidal waveform from 'continuous tension.
Control system intended for a sensorless polyphase brushless motor according to claim 1 characterized in that said overload detection means comprises a circuit for measuring the total current consumed by the N phases of the motor.
Control system intended for a polyphase brushless motor without sensor according to claim 1 characterized in that said overload detection means comprises a sampling resistor and means for measuring in said resistance, image of the total current consumed in the sum of the N phases of the polyphase motor.
Control system intended for a polyphase brushless motor without sensor according to claim 1 characterized in that said overload detection means comprises:

a means for measuring the sum of the currents (I) circulating in each of the phases (A, B, C) of the motor,

a means for calculating a threshold (E) for detecting a stop relative to the evolution of the sum of said currents (I),

a means of processing the current values (I) sampled by a mathematical or statistical operation, the threshold (E) of stop detection being determined in relation to the result of this processing.
Control system intended for a sensorless polyphase brushless motor according to claim 1 characterized in that said means for determining an operating point (34) comprises an interface for receiving a signal supplied by an external conditions sensor (40 , 41).
Control system intended for a polyphase brushless motor without sensor according to the preceding claim characterized in that the external conditions sensor (41) is a temperature sensor.
Control system intended for a sensorless polyphase brushless motor according to claim 5 characterized in that the external conditions sensor (40) provides a measurement of the supply voltage of the switching means (32).